Greets!
Me too, but the best advice I ever got was at age 10: it's not what you know, but who you know, so at the time had an excellent memory and long story short, decided to become one the hard way, working up through the ranks in a custom design manufacturing plant, though the degreed eng. that mostly just checked/rubber stamped my work still made more $$/perks annually than me.
FWIW, the T/S math I was referring to gets you 'close enough' to Scott's in room calculation/measured?.
Progress update. Initial testing is very promising!
Listening notes (as ridiculous as it is with leaks everywhere).
Mids and highs are what I expected from P7.2HD, but with some vague warts - a tiny bit of harshness on certain female vocal notes, perhaps more on male vocal notes. This could be anything, including (but not limited to) the fact that my source for testing is a $7 PCM5102A DAC fed I2S from an Rpi. I’m ignoring it for now. If the warts are still there after glue-up, with a proper source, I will play with the lining in the pressure chamber.
Bass? Well, there’s plenty of it, but it’s a bit murky on some notes and a bit boomy on others. No surprise, considering the leaks everywhere and the complete lack of knowledge on room nodes, etc. The test room isn’t even the final destination so there’s really not point. Ultimately, I am sure I can get it all dialled in once everything is glued up solid.
There are plenty of people who would think it sounded just fine the way it is, including my wife, hahah! One thing I will note; I think I might miss the power headroom of having 2x P7.2HD per speaker, as I did in my microTowers. The jury is still out.
Mids and highs are what I expected from P7.2HD, but with some vague warts - a tiny bit of harshness on certain female vocal notes, perhaps more on male vocal notes. This could be anything, including (but not limited to) the fact that my source for testing is a $7 PCM5102A DAC fed I2S from an Rpi. I’m ignoring it for now. If the warts are still there after glue-up, with a proper source, I will play with the lining in the pressure chamber.
Bass? Well, there’s plenty of it, but it’s a bit murky on some notes and a bit boomy on others. No surprise, considering the leaks everywhere and the complete lack of knowledge on room nodes, etc. The test room isn’t even the final destination so there’s really not point. Ultimately, I am sure I can get it all dialled in once everything is glued up solid.
There are plenty of people who would think it sounded just fine the way it is, including my wife, hahah! One thing I will note; I think I might miss the power headroom of having 2x P7.2HD per speaker, as I did in my microTowers. The jury is still out.
Tick, tock. Sealed up the holes for the wires through the back of the compression chambers with silicone caulking, and smeared it all over the exposed wires and contacts on the back of the binding posts’ cups. Waiting for it to completely cure before progressing to “the pouring of sand into the void” (I assume an infinite amount of sand is required, so say goodbye to all the beaches in the world).
Note: Liberal use of caulking on the exposed wires and terminals is due to the unknown composition of “sand” that I obtained, which is described as “river sand” (my comment about the beaches was a joke, if you maybe missed that🤓) and could have any number and variety of compounds and elements besides silica. Either way, it is bone dry and very dense.
Note: Liberal use of caulking on the exposed wires and terminals is due to the unknown composition of “sand” that I obtained, which is described as “river sand” (my comment about the beaches was a joke, if you maybe missed that🤓) and could have any number and variety of compounds and elements besides silica. Either way, it is bone dry and very dense.
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Sand in the void, side panel glued. Will give it a full 24 hours and then do the second one.
Nice work.
As a general observation a couple of alternatives to dried sand are dried, antibacterial cat-litter or similar. My own favourite (although stressing it's not as easy as it sounds) is expanding foam, normally used for filling in holes around pipes etc., although you normally need to keep it under some pressure (the difficult part) while it goes off to ensure an even distribution. As my friend Ed, who first put me onto this found, it extends the curing time too, which is something to be aware of.
As a general observation a couple of alternatives to dried sand are dried, antibacterial cat-litter or similar. My own favourite (although stressing it's not as easy as it sounds) is expanding foam, normally used for filling in holes around pipes etc., although you normally need to keep it under some pressure (the difficult part) while it goes off to ensure an even distribution. As my friend Ed, who first put me onto this found, it extends the curing time too, which is something to be aware of.
Hi @Scottmoose ! Thanks. I did find a few threads discussing all these options (and more) but the process of elimination resulted in plain old sand. I actively explored the kitty litter option and found that every option available in store here are the clumping type, which readily absorbs moisture. Since it is stupidly humid here most of the year, and mould issues are almost constant, I ruled that out. Figured I didn’t need anything actively trying to suck in moisture, despite being “sealed” in a plywood cavity. The expanding foam (window and door type) was a very intriguing option with the obvious advantage of being very light. However, it goes for about $17 per can here and I was unsure whether one can would be sufficient. I did use the same stuff to seal up some large gaps in my home where the geckos were getting in, and I felt like the cans ran out rather quickly.
In the end I got paralysis by analysis and then said “stuff it” and bought 20kg of sand for $3 (the beach is a 50 minute drive, so it would have cost more in fuel). I figure the weight will help it stay “planted” and “solid” which are never bad things with speakers, IMHO. My future self may curse me for the decision to add the extra kilos, but “that’s the way she goes”.
Speaking of geckos (and mice and spiders, and roaches, and…), it will be basically mandatory for me to prevent infestation through the mouths of these speakers. I have a tentative plan to apply polypropylene screen (like on any door or window screen) to the backs. Any thoughts on that would be helpful.
In the end I got paralysis by analysis and then said “stuff it” and bought 20kg of sand for $3 (the beach is a 50 minute drive, so it would have cost more in fuel). I figure the weight will help it stay “planted” and “solid” which are never bad things with speakers, IMHO. My future self may curse me for the decision to add the extra kilos, but “that’s the way she goes”.
Speaking of geckos (and mice and spiders, and roaches, and…), it will be basically mandatory for me to prevent infestation through the mouths of these speakers. I have a tentative plan to apply polypropylene screen (like on any door or window screen) to the backs. Any thoughts on that would be helpful.
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I just hope they 'killed' it in the drying process otherwise its bacteria can come back to haunt you.
Re screen, from long experience if not SS, then synthetic pet screen as it's not only cheap, but as I learned the hard way the heavy duty version can withstand the weight/viciousness of ~25 lb rabid male Raccoon trying to chew through it while clinging to it, though of course you only need the fine mesh bug version normally supplied for screen doors.
Re screen, from long experience if not SS, then synthetic pet screen as it's not only cheap, but as I learned the hard way the heavy duty version can withstand the weight/viciousness of ~25 lb rabid male Raccoon trying to chew through it while clinging to it, though of course you only need the fine mesh bug version normally supplied for screen doors.
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FWIW displacing some of the airspace with a 'cloud' of baking soda powder will solve any potential long term gas build up.
+1 for GM's suggestion about pet-screen / bug mesh. About the best you're likely to find, especially at a decent price. 👍
I really love foam for the entertainment value, but it's a very sticky messy material to work with if you are trying to make a nicely finished speaker. I think sand is the better choice here. No experience with kitty litter in speaker building, but as a cat owner I think it isn't nice to be around and I wouldn't use it for a loudspeaker.
Love this build. Looks nice.
Love this build. Looks nice.
Aaaaaah, that is quite different from consumer kitty litter nowadays. This is what you throw over oil spills in a garage, right?
.......or under all pre '68 USA and all but one brand/model of UK/European vehicles I've kept more than a few hours. 
Thanks! After all this work, I do sort of regret not making more of an effort to locate some Baltic birch, or something very much like it. The consistency of the material that I chose is not perfect by any means. They definitely look “DIY” at this point, but at least people will believe that I built them myself.
After thorough testing and tuning in the listening room, I will decide whether these speakers are up to the role in my primary system. The answer to that will determine how much money and time will be spent on finishing the exterior surfaces.
I finished up the second one yesterday and it’ll be cured by midday today, so they will be moved to the listening room and testing will begin this afternoon. Very excited!
Ain't that the truth, at least until the '80s. And sometimes a bit later. We had a bunch of Maestros here in the '80s. The oil came out about as quickly as you could pour it in. They were beige too........or under all pre '68 USA and all but one brand/model of UK/European vehicles I've kept more than a few hours.
Remember you'll likely need to trim the damping to suit the system & individual room positions; these are (when optimally loaded) high gain designs by, er, 'design' since it a/ gives some positioning flexibility, and b/ it's always easier to reduce an excess than increase what doesn't exist in the first place. 😉